Do tab-reparenting tasks after native is fully initialized

Similar to crrev.com/c/2606874, add an extra check to avoid calling
feature list before native is initialized.

Bug: 1162510
Change-Id: I6f45bc0dbd7081abd41c105223f4b312d0af5ddb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2645506
Commit-Queue: Lijin Shen <lazzzis@google.com>
Commit-Queue: Theresa  <twellington@chromium.org>
Auto-Submit: Lijin Shen <lazzzis@google.com>
Reviewed-by: Theresa  <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846372}

chrome/android/java/src/org/chromium/chrome/browser/app/ChromeActivity.java

@@ -2431,7 +2431,8 @@ public abstract class ChromeActivity<C extends ChromeActivityComponent>
         // Note: order matters here because the call to super will recreate the activity.
         // Note: it's possible for this method to be called before mNightModeReparentingController
         // is constructed.
-        if (ChromeFeatureList.isEnabled(ChromeFeatureList.ANDROID_NIGHT_MODE_TAB_REPARENTING)
+        if (FeatureList.isInitialized()
+                && ChromeFeatureList.isEnabled(ChromeFeatureList.ANDROID_NIGHT_MODE_TAB_REPARENTING)
                 && mTabReparentingController != null) {
             mTabReparentingController.prepareTabsForReparenting();
         }